function [K,Pout] = kalman_filter_jodesph_devries_observational_update(z,R,H,P) 
% 
% Joseph "stabilized" Kalman filter measurement 
% update as implemented by De Vries. 
% 
T1 = P*H'; 
T2 = H*T1 + R; 
K  = T1/T2; 
T3 = .5*K*T2 - T1; 
T4 = T3*K'; 
Pout = P + T4 + T4'; 
 